1. Field of the Invention
The present invention relates to a metallic plate material which is a material for, for example, a casing for containing, parts of an electric/electronic instrument. More specifically, the present invention relates to a metallic plate material which comprises a resin-coated metallic plate material being good in earthing properties, shield properties against electromagnetic waves, formabilities, sliding properties, resistance to solvents, etc.
2. Prior Art
Generally, for example, a casing for containing parts of various kinds of electric/electronic instruments is produced by, for example, forming a metallic thin plate having a surface coating.
In forming performed in that case, it has become general to use volatile press oil in order to omit a process of cleaning after press-molding. Therefore, it is required that the resin-coated metallic thin plate should have good formabilities. In some cases, press-molding is preformed using ordinary press oil, and in that case, solvent degreasing needs to be performed after press-molding. Therefore, it is also required that the metallic thin plate having a surface coating should have resistance to solvents.
For a casing of a machine wherein modular components are frequently attached to or detached from a main body, like a personal computer wherein an integrated-type disc drive is attached to or detached from a main body in a casing, it is required that the surface of the metallic thin plate having a surface coating should have good sliding properties.
Further, in order that the appearance of a casing may not be deteriorated by fingerprints and flaws when an instrument is assembled, it is required that the casing should have resistance to fingerprints and resistance to scraches.
Thus, a resin-coated metallic thin plate having a surface coating used for producing a casing for an electric/electronic instrument needs to be good in formabilities, resistance to solvents, sliding properties, resistance to fingerprints, resistance to scratches, etc.
In order to meet the requirements as above, a resin-coated metallic plate material is used. However, generally, a resin coating is insulator. Therefore, a casing made of a resin-coated metallic plate material cannot be earthed, and cannot satisfactorily exhibits a shield function properties against electromagnetic waves from electric/electronic circuits of parts of an electric/electronic instrument contained in the casing.
The shield properties against electromagnetic waves and earthing properties of the resin-coated metallic plate material can be improved by improving the electrical conductivity of the resin coating, or in other words, decreasing the degree of the electrical resistance thereof. Thus, in order to deal with the above-mentioned problems, there has been proposed a resin-coated metallic plate material which contains, as a major component, water-soluble polymer wax having an electrically-conductive auxiliary agent such as metallic soap, metallic powder, or graphite powder mixed into (see Japanese Unexamined Patent Publication No. Hei 5-320685).
There has been also proposed a resin-coated metallic plate material to which metallic particles are added (see Japanese Unexamined Patent Publication No. Hei 9-255759, Japanese Unexamined Patent Publication No. Hei 11-140345, etc.).
However, the prior art as above has the following problems:
For example, when a metallic plate material is formed, an electrically-conductive agent such as metallic powder contained in a resin coating may fall off by the resin coating, which forms a surface of the metallic plate material, being rubbed by a molding machine, and/or by the plate material being transformed. The metallic powder that has fallen off may come into electric circuits or precision drive portions of parts of an electric/electronic instrument in a casing, and make the electric/electronic instrument malfunction.
Further, the resin coating of this type has electrical conductivity only at the places where the electrically-conductive agent exists. Since the shape and distribution of the electrically-conductive agent affects the electrical conductivity, the electrical conductivity varies to a large degree, according to the place. Therefore, the casing made of this plate material does not allow an electric/electronic instrument to be earthed at every desired place. The electric/electronic instrument may not be able to be earthed at some place of the casing.
An object of the present invention is to provide a metallic plate material coated with an electrically-conductive resin coating which does not contain an electrically-conductive agent in the form of particles, and which is good in earthing properties, shield properties against electromagnetic waves, formabilities, sliding properties and resistance to solvents, and provide an electric/electronic instrument using this metallic plate material.
In order to attain the above object, the present invention provides a metallic plate material for an electric/electronic instrument comprising a resin-coated metallic plate material, wherein the resin coating contains, as resin, at least one substance chosen from a group consisting of acrylic-based resin, epoxy-based resin, and urethane-based resin, and contains water in the amount of 1 to 50 mass % and a lubricant in the amount of 0.1 to 20 mass %, and the resin coating has a thickness of 0.05 to 5 xcexcm.
Further, the present invention provides an electric/electronic instrument using this metallic plate material.